Objectives: We outline, quantify, and attempt to reduce the sources of variation that may influence prospective functional imaging approaches to studying the neuropathophysiology of mild traumatic brain injury. Hypothesis: BOLD signal variability in a single subject can result in significant between-session differences. Quantifying this variability will aid in establishing new, appropriate statistical criteria. Variability will be reduced when employing a parametric approach. Participants: Between-subject variability was assessed using a single recording session from each of 8 different college students. Within-subject variability was assessed using 2 subjects each studied over 9 sessions. Methods: A session consisted of 3 finger-sequencing tasks and an NBack memory task. F tests quantified the contribution of between-subject variance. Permutation methods provided a measure of the magnitude of within-subject differences expected by chance. Results: Within-subject variability was small requiring a slight increase in the statistical threshold for detecting true session differences. This variability was reduced when parametric measures that quantify the pattern across task levels were compared. Conclusions: The research underscores the increases sensitivity of a prospective functional imaging approach and its potential advantage over group approaches for understanding the neurofunctional basis of mild brain injury and recovery of function.

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